Compensated paralleling system



June 10, 1930. 1 THOMAS 1,763,276 I CQMPBNSATED PARALLELING SYSTEM Filed Sept. 19, 1927 I I M INVENTOR P/I/W/ps T 170mg:

- A'TTORNEY Patented June 10, 1930 UNITED STATES FFIC'E PHILLIPS THOMAS, OF EDGEWOOD, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA COMPENSATED PARALLELING SYSTEM Application filed September 19, 1927. Serial No. 220,556.

This invention relates broadly to an instantaneous paralleling relay system having completed voltage compensation.

The principal object of this invention is to proiide means for paralleling parts of the same alternating-current distribution system and also to provide a scheme that may serve as a phase-unbalance relay.

A further object of this relay scheme is to provide a svstem by which paralleling of two branches of the same altemating-current distribution system shall be effected whenever the voltages of the two branches are of normal value and in phase.

A further object of this relay system is to provide for the paralleling of the two branches of a distribution system upon phase coincidence of the voltages of the branches, if the voltage of one branch is normal and the voltage of the other branch below normal or if both are below normal, whether equal or not.

Another object of this invention is to prevent paralleling of two branches of an alternating-current system even if the voltages thereof are in phase it the voltage of one is normal and that of the other above normal, or if both voltages are above normal, whether equal or not.

Another object is to provide a relay system which shall prevent paralleling of two alter hating-current circuits when the phase voltages of one circuit assume unsymmetrical phase positions.

The relay system which I have devised to accomplish the above objects is shown diagrammatically in the single figure of the accompanying drawing.

In the drawing I have indicated two branches of an alternating-current distribution system at 1-2 and 34, or lines 1, 2 and 3, 4 may be low tension leads from potential transformersconnected to the two branches. The conductors 1 and 3 are connected by the conductor 5. Across the two branches are connected the transformers 6 and 8, respectively, while transformer 7 is connected, through transformers 6 and 8, to the lines 2 and 4 of the two branches. This scheme of connections causes the resultant of the voltages of the two branches 1-2 and 3-4 to be impressed upon the primary of the transformer 7.

The transformers 6, 7 and 8 supply alternating currents to rectifiers 9, 10 and 11, respectively. The direct-current terminals of the rectifier-s are connected in series and supply current to a local circuit consisting of battery 13 or any equivalent source of constant I). C. potential, the operating coil of the switch 14 and the resistance 12. The polarity of the battery 13 is opposed to that of the rectifiers 9, 10 and '11. Closure of the contacts 15 may effect the paralleling of the two branches of the distribution system directly or may close another local circuit including the operating coil of the paralleling switch.

In the embodiment of my invention described herein, the switch 14 serves as a control relay for the switch 16 which, when operated by the energization of its closing coil, connects the circuits 12 and 34 in parallel.

The operation. of this relay system will now be described.

Assuming first that the voltages of the branches 1-2 and 3 4 are both normal and in phase, transformers 6 and 8 will have the voltages of the two branches impressed upon them, while transformer 7 will have no voltage across its terminals since it is subject to the resultant of the voltages of the two branches and, since, whenever the voltages of the two branches are equal and in phase, their resultant is zero. This follows from the fact that, since both branches are fed from the same generating source, the voltages thereof are always in synchronism. Because of the voltages induced in the secondaries of transformers 6 and 8, unidirectional voltages will appear across the direct-current terminals of rectifiers 9 and 11, and the sum of these voltages will be impressed upon the local circuit, including the switch 14, but will be opposed by the voltage of battery 13. The voltage of the battery 13 is adjusted to be larger than that "from rectifiers 9 and 11 in series, so that with normal voltages on both branches of the alternsting-current distribution system, the difference between the battery voltage and that of the rectifier-s in series will be suflicient to operate the switch ll to cause the two branches of the system to be par: llcled.

The function of resistance 12 is to permit current from battery 13 to energize the coil of swuch let when the sum of the voltages of rcctitiers 9 l0 and 11 is sutiiciently small.

Now. it the volta 'e of one of the branches rises to a value above normal, while that 0i the other remains at its normal value, the volta BIC impressed upon the local circuit by the rectitiers will be sharply increased, because of the increase in the volta of: that particular branch, the voltage of which is above normal and also because of the resultant voltage im pres: d upon the transformer 7. This willrcsuit in a Q'rea voltage u Jon the local cirend in opposition to that of the battery 13.

and therefore, oper: tion of the switch bl will be prevented. since the dillerence between the hattz voltage and the sum (it rectifier voltages is now insntzicient to operate the switch.

It, however, the voltage of one branch decreases oelow normal, while the other remain normal. the voltage upon the local circuit ill be just the same as it was when both were normal. This due to the tact that, whenever the voltage of either branch decreases, although the voltage on the transformer connected to that branch also decreases, the voltage upon the tr; nstormer 'T is in reased by just the same amount, thus causing conditions in the entire system to remain unchanged. As a result of these conditions, the switch ll will be oiwratcd just as in the case where both branches of the distribution system had normal voltage thereon.

Another ot the above described scheme ol ogwration is that it permits paralleling; at wider phase angles between the voltaa'er t one of them is below normal. This voltage-compelmating action is more tully described in my copendine appli "ation Serial W146i. tiled Oct. 20. 19:37.

rcsul t n my when the voltages of the two branc tea are both normal but also whenever these voltages are equal and below normal. This is apparent from the fact that, whenever the nz-ltages ot the two b 'anches are equal, the transformer 7 ha no voltage impressed upon it and, therefore, the rectifier 10 does not sup ply any direct-current voltage to the local circult and, as previously stated. the directcurrent voltages from the 'ectifiers 9 and 11 a 'e not suliicient to prevent the switch it from being: operated by the voltage of the battery 13. it the voltage. are equal and below nori ial.

it the voltages of both branches, however, are above norr. al, the sum of the rectifier voltages will be increased sutliciently to prevent operation of switch 14 by the voltage of battery 13v This will be the case even should both the voltages increase by the same 2 mount, so that transformer 7 and rectifier 10 would not be eli'eetive to add any direct current voltage to oppose that (it batc y 13. It only one of the voltages increases above normal, however, the increz se in the sum of the rectifier voltages will be greater than it both the branch voltages increased by the name anmunt, because of the added etl ct ol. transformer 7. A. a result, switch 14. will not be energized when both volta are above normal. whether equal or not.

It conductors l2 and 3- represent corresponding phase branches ot a polyphase distribution system, the voltages 0n transformers 6 and S will be those of the corresponding phases, and the voltage on transform '4' will he the resultant of the phase volt ages, as explained ab ve. Under these conditions, it, for any roe-1m, either or" the branches bec mes unbalanctal so that the neutral point shifts, paralleling will be prevented because at the tact that the direct current resulting from the phase vol es phi-i that trom their resultant. prevents operation of the switch 1%. Parallelinn' will take place only wh n the two branches ot the system are balanced and when the voltages of the branches have the relations previously in dicated. i. e.. when the branch voltages are equal and normal or below or when the h anch voltages are unequal but neither is above normal.

Various modifications in the system, and in the ar 'angz ement and location o'l parts may he made within the spirit and scope oi my in vention and such modifications are intended to be covered by the appended claims.

I claim as my invention:

1. A system tor connecting a pair of altcr uating-current circuits comprising;- a mag netically operated circuitconnector, a control relay therefor, a direct-cmrentsource for energizing said relay and means for setting: up a voltage to oppose the energization of said relay in proportion to the voltages of said circuits and in proportion to the instantaneous resultant thereof, whereby said circuits will be connected whenever the voltage of one is below normal, and that of the other is normal and in phase with the voltage of the first mentioned. circuit.

2. A system for connecting a pair oi alternating-current circuits comprising a magnetically ope 'ated circuit closer, a control relay therefor, a direct-current source for energizing said relayother direct-current sources in series opposition to said first-inentioned source for opposing the energization of said relay in proportion to the voltages of said circuits and the instantaneous resuit-ant thereof. whereby said circuits will be connected at all times when the voltage of one is normal, and the other below normal or when both voltages are equal and not above normal, it said voltage are in phase.

3. A system for connecting alternatingcurrent circuits comprising a connecting switch, a relay for controlling said switch a source of direct-current for energizing said relay, rectifiers connected across said circuits and a rectifier connected between said circuits, the output of said rectificrs being connected in series opposition to said direct-current source, whereby said relay is energized to close the connecting switch whenever the voltages of said circuits are equal, and not above normal and whenever one of the voltfor producing a direct-current voltage proportional to the voltages of the circuits and proportional to the instantaneous resultant thereof, a source of constant opposing directcurrent voltage, and the closing coil of a relay for controlling the connection of said circuits, the value of said opposing voltage being of suflicient magnitude to energize the said closing coil to the operative value whenever the voltage of one or both circuits is normal or below and in phase with that of the other circuit but insuflicient to energize said closing coil if the voltage of either of said circuits is above normal.

5. A system for connecting alternatingcurrent circuits comprising a circuit closer For connecting said circuits. a source of current having a predetermined voltage, controlling means for said circuit closer adapted to be energized from said source of current, and means for developing a voltage opposing the energization of said controlling means in proportion to the voltages of the circuits and their instantaneous resultant, whereby the said circuits will be connected whenever their voltages are normal and in phase or below normal and in phase.

6. In a system for connecting a pair of alternating-current circuits comprising a circuit closer for connecting said circuits, a source of current having a predetermined voltage, a relay for controlling said circuit closer and adapted to be energized from said source of current. and means for opposing the energization of said relay by a voltage that is proportional to the voltages of said circuits and in proportion to the instantaneous resultant thereof, whereby the circuits will be connected whenever the voltages are both below normal and in phase.

7. A system for connecting a pair of alternating-current circuits comprising a magnetically operated circuit-connector, a source of direct-current supply having a predetermined constant voltage, a control relay for said circuit connector adapted to be energized from said current source, and means for developing a voltage to oppose the energization of said relay in proportion to the voltages of the circuits and their instantaneous resultant, whereby said. circuits will. be connected when the voltage of one is normal and that of the other subnormal and the voltages are in phase or when both are equal, not above normal and in phase.

In testimony whereof, I have hereunto subscribed my name this 12th day of September,

PHILLIPS THOMAS. 

